Ravi Teja Seethamraju PhD, Presenter: Employee, Siemens AG Stockholder, Siemens AG

Iga Muradyan, Abstract Co-Author: Nothing to Disclose

Aida Faria, Abstract Co-Author: Nothing to Disclose

Donna Oka, Abstract Co-Author: Nothing to Disclose

Ritu Randhawa Gill MBBS, Abstract Co-Author: Nothing to Disclose

DCE imaging of the thorax with 3D Radial VIBE sequence can acquire free breathing acquisition without registration. The resulting pharmacokinetic maps are of higher diagnostic value than current standard 2D or 3D FLASH acquisitions.

CT is currently the imaging modality of choice to non-invasively evaluate thoracic diseases. Due to growing concern for radiation exposure, dynamic evaluation is limited with CT. While MR is widely gaining ground as the modality of choice in such applications, it suffers from two major issues namely, susceptibility and motion. While susceptibility can be reduced by shortening echo times, it is difficult to achieve optimal motion compensation when fast time resolution is required for reasonable pharmacokinetic analysis. Here we demonstrate that with a 3D GRE sequence that is acquired as a radial stack of stairs for DCE imaging, it is possible to overcome both the difficulties. The sequence is very robust to motion and aliasing. Since the k-space is updated for every radial line it is ideal for dynamic acquisitions.

The 48 time points acquired with the 3D radial VIBE sequence did not require any registration between the time points. As shown in the figure 1 the free breathing 3D radial VIBE compares reasonably well with a coronally acquired breath held VIBE sequence. It can seen from  the time course (1c) for the ROI in red (1b) is very tight with very little deviation from the resulting fit with a Tofts model. The maps for Ktrans, Kep and iAUC are very clean thereby enabling more accurate and reproducible parameters.

In an IRB approved study, 6 patients with mesothelioma were scanned on a 3T scanner (Trio a Tim System, Siemens Healthcare, Germany) after administration of 0.1mmol/kg of Magnevist (Bayer Healthcare, USA). Dynamic acquisitions were acquired coronally with a 3D radial VIBE sequence with a TE=1.5ms and TR=3ms. The voxel dimensions were set to be 2mm isotropic and with a time resolution of 3s for 48 time points. Other morphological scans included Cartesian VIBE in coronal orientation with high in-plane dimensions. Pharmacokinetic analysis was performed on commercial software (Tissue4D, Siemens Healthcare, Germany).

Seethamraju, R, Muradyan, I, Faria, A, Oka, D, Gill, R, Registration Free Pharmacokinetic Analysis of Mesothelioma with Free Breathing 3D Radial MRI.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14014809.html